As memory densities increase, the bit size for recording media decreases. As a result, the critical dimensions of readers and writers decrease. For example, magnetoresistive (MR) elements are often used in higher density read heads. As the memory density of recording media increases, the critical dimension of the magnetoresistive element, which correspond to the track width, decreases. Thus, new methods for fabricating such structures are desired to be found. For example, conventional MR elements have been fabricated using an undercut bilayer mask. The bottom layer of the bilayer mask has a smaller width, or critical dimension, than the upper layer. However, at smaller critical dimensions on the order of 0.06-0.08 μm or less, significant issues are encountered. For example, the bilayer mask tends to collapse. In addition, the track width becomes difficult to control. Consequently, yield is reduced.
In order to address such issues, it would be desirable to use a single layer photoresist mask. FIG. 1 depicts a conventional method 10 for fabricating a MR device. FIGS. 2A-2F depict a conventional MR device 50 during fabrication. Referring to FIGS. 1-2F, the layers of the MR element are provided, via step 12. Typically, step 12 includes sputter depositing the layers for a spin valve or other analogous giant magnetoresistive (GMR) element. These layers are typically on the order of three hundred and seventy Angstroms thick. A planarization stop layer, typically a diamond-like carbon (DLC) layer, and dielectric antireflective coating (DARC) layer are deposited, via step 14 and 16, respectively. The DLC layer is typically on the order of one hundred fifty to two hundred Angstroms thick. A layer of photoresist is provided on the device, via step 18. The photoresist layer is typically on the order of two thousand two hundred Angstroms thick. Thus, the thickness of all of the layers is typically on the order of two thousand seven hundred Angstroms thick. FIG. 2A depicts the conventional MR device 50 formed on a shield 52 and including MR element layers 54, DLC layer 56, DARC layer 58, and photoresist layer 60. Although depicted as a single layer, the MR element layers 54 typically include a laminate of multiple layers.
A single layer photoresist mask is developed from the single layer of photoresist 60, via step 20. FIG. 2B depicts the MR device 50 after formation of the single layer photoresist mask 60′. The mask 60′ includes a portion 65 that covers the device area 67. The MR element is to be formed in the device region 67. The mask 60′ also includes portions 63 and 64 and has apertures 61 and 62 therein. The apertures 61 and 62 and portions 63 and 64 cover the field areas 66 and 68 of the MR device 50. Typically, the field areas 66 and 68 cover approximately ninety percent of the conventional MR device 50, while the device area 67 occupies approximately ten percent of the conventional MR device 50.
The portions of the layers 56 and 58 exposed by the apertures 61 and 62 are removed, via step 22. Step 22 is typically performed using a reactive ion etch (RIE). FIG. 2C depicts the MR device after step 22 is completed. Thus, the portions 56′ and 58′ of DLC and DARC layers remain. In addition, a portion of the MR element layers 54 are exposed by the apertures 61 and 62.
The MR element is then defined, via step 24. Step 24 typically includes performing a critical junction ion mill. During the ion mill, some or all of the photoresist mask 60′ and underlying the DARC layer 58′ may be removed. FIG. 2D depicts the conventional MR device 10 after step 24 is completed. Thus, the MR element 70 has been formed from the MR layers 54. The MR element 70 has a critical dimension CD. In addition, portions 54′ of the MR layers remain. These portions 54′ of the MR layers reside in the field areas 66 and 68, and are not typically used as a device.
An insulating layer, a hard bias layer, and a capping layer are typically deposited, via step 26. The hard bias layer and capping layer are preferably blanket deposited. FIG. 2D depicts conventional the MR device 50 after step 26 is completed. Thus, the insulating layer 71, hard bias layer 72 and capping layer 74 are shown. Although the hard bias layer 72 and capping layer 74 appear discontinuous, each appearing almost as two separate layers in FIG. 2D, this phenomenon is due to the underlying topology of the conventional MR device 50.
The conventional MR device 50 is planarized, via step 28. Typically step 28 is performed using a chemical mechanical polish (CMP). FIG. 2F depicts the conventional MR device 50 after step 28 has been completed. As a result of the CMP, the top surface of the conventional MR device 50 is flat. Thus, using the conventional method 10, the conventional MR device 50 is fabricated. The conventional method 10 may allow for removal of a “liftoff” step for the photoresist mask 60′. Thus, fencing may be eliminated. In addition, overspray for a tunneling magnetoresistive element may be avoided. Consequently, contact resistance may be better controlled and have a lower variation. In addition, a smaller critical dimension may be directly printed on the photoresist mask 54′ and provided for the conventional MR element 70.
Although the conventional method 10 may for the conventional MR device 50, one of ordinary skill in the art will readily recognize that there may be serious drawbacks. Delamination of the MR layers 54 may occur for areas of the conventional MR device 50 on which a stop layer, such as the DLC layer 56′, is provided. This delamination adversely affects yield of the conventional MR device 50. Furthermore, during definition of the MR element 70 in step 24, the relatively high thickness of the stack of layers 54, 56′, 58′, and 60′ may result in shadowing. This shadowing may cause asymmetries in the conventional MR device 50, which are undesirable. Furthermore, the topology of the conventional MR device 50 during the CMP in step 28 may result in a non-uniform CMP. Consequently, in contrast to the MR device 50 depicted in FIG. 2F, the surface of the conventional MR device 50 may not be as flat as desired. Consequently, like the use of a bi-layer mask, the conventional method 50 may not be able to fabricate an MR device at higher memory densities and smaller critical dimensions.
Accordingly, what is needed is an improved system and method for providing an MR device suitable for higher memory densities